Pronouns aren't the only pro-forms

The way pronouns work is familiar to everyone. If someone has just mentioned the old man with green hair who lives in an apple tree by the lake, you can save some time by using he and him to refer to him afterwards.

But pronouns are a special case of a more general category known as pro-forms. While pronouns stand in place of noun phrases (NPs), other pro-forms stand in place of preposition phrases (PPs), verb phrases (VPs) and adjective phrases (APs). Some examples:

A PP pro-form:

• Jill will stay at the hotel.
• Penny will stay there too. [there interpreted as at the hotel]

A VP pro-form:

• Jill will stay at the hotel.
• Penny will do so too. [do so interpreted as stay at the hotel]

An AP pro-form:

• Jill was angry with the priest.
• Penny was even more so. [so interpreted as angry with the priest]